MutableLazy

MutableLazy.kt

package com.bitgrind.scrabble.ext

import kotlin.concurrent.atomics.AtomicReference
import kotlin.concurrent.atomics.ExperimentalAtomicApi
import kotlin.reflect.KProperty

fun <T : Any> mutableLazy(initializer: () -> T) = MutableLazy(initializer)

/**
 * A PUBLICATION-style atomic lazy that’s also mutable.
 *
 * The initializer *may* be called multiple times, but
 * only the first result is stored and is returned to
 * all callers.
 */
@OptIn(ExperimentalAtomicApi::class)
class MutableLazy<T : Any>(val initializer: () -> T) {

    private val valueRef: AtomicReference<T?> = AtomicReference(null)

    @OptIn(ExperimentalAtomicApi::class)
    operator fun getValue(thisRef: Any?, property: KProperty<*>): T {
        return valueRef.load() ?: let {
            val initValue = initializer()
            valueRef.compareAndExchange(null, initValue) ?: initValue
        }
    }

    operator fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
        valueRef.store(value)
    }

    fun clear() {
        valueRef.store(null)
    }
}